Electric boxes are mounted in walls to support electrical outlets such as duplex outlets, light switches, and the like, along with a wide variety of other electrical components. In walls formed with wood studs, it is typical to simply screw or nail an electric box to the stud. With walls formed from metal studs, and particularly in commercial buildings, the electric boxes tend to be supported by brackets that attach either to the floor or to a metal stud.
The electric boxes can be supported in several different ways. They can be supported on a bracket that rests on the floor, they can be supported on a bracket that attaches directly to a metal stud, or they can be attached between two metal studs, which would require something that bridges the metal studs. This requires the manufacturer to have at least three separate mounting brackets that must be supplied to the construction site.